Cooking appliance door with an inner borosilicate glass door pane and cooking appliance with said door

ABSTRACT

The cooking appliance door has an inner door pane made of borosilicate glass and a paint layer applied to a surface on one side of said inner door pane. The paint layer is made by printing high-temperature-resistant non-enamel paint with an organic or inorganic binder on the surface on the inner door pane, preferably by a screen printing technique. In order to prevent the deformation of the printed inner door pane during hardening, the paint layer consists of a plurality of individual paint spots with a predetermined maximal geometric shape. The individual paint spots are arranged in a predetermined pattern with a predetermined paint-free spacing from each other on the inner door pane.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a cooking appliance door with an inner door pane made of borosilicate glass, on which at least one paint layer comprising high-temperature-resistant non-enamel paint with an organic or inorganic binder is applied. The invention also relates to a cooking appliance with a door of this type.

2. Description of the Related Art

A household cooking appliance, especially a baking oven, has a cooking compartment with an opening, which is closable by a cooking appliance door with a viewing window. Cooking appliances with a door that is completely glass are also known. A baking oven with an oven muffle acting as cooking compartment is a typical currently known household appliance. This sort of baking oven has been currently equipped to a large extent with a pyrolytic self-cleaning means, by which cooking residues are decomposed to ash at pyrolysis temperatures above 500° C.

The typical household cooking appliance door and thus its viewing window is of course heated during operation due to the comparatively high temperatures in the cooking compartment of the cooking appliance. Cooking appliance doors, which are entirely glass and which typically each comprise a glass pane packet, are also heated during operation of cooking appliances having such full glass appliance doors. The same is true to an even greater extent during the pyrolysis occurring at extremely high temperatures in baking ovens. High-quality glass is used for door panes of cooking appliances because of this high heat load. This is particularly true for the viewing windows or full glass doors for cooking appliances and baking ovens with pyrolytic self-cleaning means. A pre-stressed borosilicate glass is thus used for the inner door pane that is closest to the oven muffle. This sort of glass is characterized by a special resistance to high temperatures.

In order to keep the temperature on the outer side of the viewing window or full glass door of the cooking appliance as low as possible to reduce the danger of burns and other injuries due to contact with the outer surface of the viewing window, the viewing window is provided with a coating that reflects heat into the interior of the cooking compartment, i.e. an infrared-reflecting coating. An observation window described in U.S. Pat. No. 4,898,147 has an inner door pane made from borosilicate glass with an infrared-reflecting multilayer coating and noble gas layer between the inner and outer door panes, in order to reduce the heat transferred. A so-called “cold door” for a pyrolysis-baking oven is thus provided by means of these features. This “cold door” is defined by GIFAM DOC 266/01 by stating an upper limiting temperature, which the contacting surface of the door can have, when the outside temperature is 23° C. and the temperature in the cooking compartment is about 500° C. (with glass, less than 70° C.).

Furthermore it is known to provide the borosilicate glass inner door pane with printing made from enamel paint, comprising special writing (letters, words) and symbols, especially usage hints for the operators, particularly which indicate different cooking programs. This printed information can be located on the side of the inner door pane facing the door interior and also on the side facing the cooking compartment, as described in DE 100 07 923 C1. DE 101 43 925 A1 discloses a suitable borosilicate inner door pane for a cooking appliance door printed with enamel paint.

Conventional enamel paints melt or fuse with the glass surface during burning on the borosilicate inner door pane. Stresses are developed in the glass-door pane due to the differing thermal expansion properties of the glass door pane and the enamel paint printing under strong thermal loads. These stresses occur in connection with interactions (ion exchange) between the enamel paint, a glass flux-based colored printing, and the borosilicate glass. Because of that the impact strength of the glass door pane is reduced for impacts on the side facing away from the printed information. For that reason the above-mentioned DE 100 07 923 C1 suggests that the color printing printed with the enamel paint should be applied to the impact-endangered outside of the inner door pane facing the interior of the cooking compartment. Since the current enamel paints are not heavy-metal-free, especially not lead-free, there is a danger that the heavy metals, especially lead, could be volatilized in the cooking compartment at higher operating temperatures because of the color printing on the exposed side in direct contact with the cooking compartment. Furthermore the enamel paint coating has a rough, unpleasing surface.

There is no enamel print or enamel for printing currently known for borosilicate glass, which (1) is heavy-metal-free, (2) has a smooth aesthetically pleasing surface and (3) maintains the impact resistance of the borosilicate glass pane, when the impacts occur on the side facing away or opposite from the printing. As a result, non-enamel paint with organic (e.g. silicones or fluoropolymers) or inorganic (e.g. water glass; sol-gel binders) binders was developed, which in contrast to the conventional enamel paint is not bonded with the glass surface by fusion. These non-ceramic paints are described in the old Patent application DE 103 13 630, whose subject matter is incorporated herein by explicit reference thereto.

This paint is only a SiO₂-based paint with carbon particles, which are coated or enveloped by SiO₂, as pigment, as is described in DE 195 25 658 C1.

The newly developed heavy-metal free non-enamel paints generally have the property that they fade or shrink due to evaporation of solvent and the glass pane deforms during the burning in process at temperatures of 670 to 730° C.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a cooking appliance door of the above-described type with an inner door pane of a viewing window, which is made of borosilicate glass and has a paint layer, in which no noteworthy deformation of the door pane made of borosilicate glass occurs during application of the paint layer.

This object and others, which will be made more apparent hereinafter, are attained in a cooking appliance door comprising an inner door pane made of borosilicate glass and at least one paint layer applied to a surface on one side of the inner door pane. The at least one paint layer comprises a high-temperature-resistant non-enamel paint with an organic or inorganic binder.

According to the invention the at least one paint layer consists of a plurality of individual paint spots each having a predetermined maximal geometric shape, which are arranged in a predetermined pattern with a predetermined paint-free spacing from each other on the surface on the one side of the inner door pane.

The cooking appliance door with the above-described paint layer has the advantage that the planar inner door pane of the cooking appliance can be heated for optimal hardening to the hardening temperature, without experiencing any noteworthy deformation.

The cooking appliance door is preferably used as a full glass door for a baking oven with a pyrolysis operating mode.

In preferred embodiments of the cooking appliance door the paint spots are arranged in a grid-like pattern comprising a plurality of rows arranged one above the other. The rows can be arranged so that respective paint spots from different rows are above each other in a corresponding column. Alternatively neighboring rows can be displaced a predetermined distance from each other, preferably half the distance between neighboring paints spots in a given row.

The shape of the paints spots is not of special importance to the invention and they can be circular, square, rectangular, oval or even irregular shaped.

The paint spots are preferably applied to the surface of the inner door pane by a printing method, especially screen printing. Preferably their largest dimension is from 1 mm to 5 mm. The free space between the paint spots must be large enough so that it remains free of paint during the printing process.

A cooking appliance that includes the cooking appliance door according to the invention is also part of the invention.

BRIEF DESCRIPTION OF THE DRAWING

The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiment, with reference to the following figures, in which

FIGS. 1A and 1B are cutaway plan views of respective inner door panes of two embodiments of a cooking appliance door according to the invention, with a regular grid-like pattern (grid structure) of circular paint spots according to the invention;

FIG. 2 is a cutaway plan view of an inner door pane of a cooking appliance door according to the invention with a regular grid-like pattern of square paint spots according to the invention; and

FIG. 3 is a cutaway plan view of an inner door pane of a cooking appliance door according to the invention with an irregular line pattern.

DETAILED DESCRIPTION OF THE INVENTION

The main inventive idea is that the above-described non-enamel paint with the organic or inorganic binder does not completely and continuously cover the surface of the door pane 1, but is applied to the door pane of the cooking appliance door 10 in the form of paint spots s, e.g. in a raster 2, 2′, 2″ 2′″ of paint points or paint spots s. Different rasters or patterns of spots s are of course possible.

The particular geometric shape of the paint spots s has no influence on the operation of the invention. The paint spots s particularly, as shown in FIGS. 1A and 1B, are circular, or, as shown in FIG. 2, they are square. However they could also be oval or rectangular, hexagonal or other geometric shapes. In addition, the paint spots s can be irregular shapes, as shown in FIG. 3.

Preferably, as shown in FIG. 1A and FIG. 2, the paint spots s are arranged in a pattern 2, 2″ with a regular grid-structure, i.e. in a series of rows r₁, r₂, r₃, etc (FIG. 1A) one above the other, so that respective paint spots s of the different rows are arranged in columns one above the other. However the paint spots s can also be arranged as shown in FIG. 1B in a staggered pattern 2′ comprising an array of rows r₁, r₂, r₃, . . . one above the other, but with neighboring rows, e.g. r₂, r₃, shifted a predetermined displacement distance from each other to form a staggered pattern 2′.

In the case of line-shaped paint spots s, especially with those of different irregular shapes, the paint spots can be arranged, as shown in FIG. 3, in an irregular line pattern 2″ on the inner door pane 1.

The paint spots s are typically printed on the inner door pane 1, preferably by screen printing. The smallest possible paint spot size obtainable by a screen printing technique here is about 1 mm. The ideal dimension of the paint spots s, i.e. with circular paint spots the ideal diameter, or with non-circular paint spots s the ideal largest length, is between 1 mm and 5 mm.

It is especially important that the dimension of the intervening space or free space between the paint spots s has a size that is sufficiently large so that it remains paint free during the printing process. The local shrinkage of the printed spots s can only be compensated by local expansion in this paint-free region

Since the new non-enamel paint is limited in regard to its scratch resistance, the printing takes place preferably on the side of the inner door pane 1 facing away from the cooking compartment. The printing of the paint spots can however-also be provided with a scratch resistance layer, especially with an IR reflecting layer. Then it can be applied to the side of the inner door pane 1 facing the cooking compartment.

While the invention has been illustrated and described as embodied in a cooking appliance door with an inner window pane made of borosilicate glass and a cooking appliance containing that door, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

What is claimed is new and is set forth in the following appended claims. 

1. A cooking appliance door comprising an inner door pane comprising a borosilicate glass; at least one paint layer applied to a surface on one side of said inner door pane, wherein said at least one paint layer comprises a high-temperature-resistant non-enamel paint with an organic or inorganic binder and said at least one paint layer consists of a plurality of individual paint spots with a predetermined maximal geometric shape, wherein said individual paint spots are arranged in a predetermined pattern with a predetermined paint-free spacing from each other on said surface on said one side of said inner door pane.
 2. The cooking appliance door as defined in claim 1, wherein said paint spots are arranged in a grid pattern comprising a plurality of rows arranged one above the other.
 3. The cooking appliance door as defined in claim 1, wherein said predetermined pattern of said paint spots is a grid-structured raster.
 4. The cooking appliance door as defined in claim 3, wherein said grid-structured raster of said paint spots comprises a plurality of rows of said paint spots arranged one above the other and neighboring rows of said paint spots are displaced with respect to each other by a predetermined displacement.
 5. The cooking appliance door as defined in claim 4, wherein said predetermined displacement amounts to half a raster line spacing.
 6. The cooking appliance door as defined in claim 1, wherein said paint spots have different geometric shapes and are arranged in an irregular line-shaped pattern.
 7. The cooking appliance door as defined in claim 1, wherein said paint spots each have a circular shape.
 8. The cooking appliance door as defined in claim 1, wherein said paint spots each have an oval shape.
 9. The cooking appliance door as defined in claim 1, wherein said paint spots each have a rectangular shape or each have a square shape.
 10. The cooking appliance door as defined in claim 1, wherein said paint spots each have a largest dimension in a range from 1 to 5 mm.
 11. The cooking appliance door as defined in claim 1, wherein said paint-free spacing between said paint spots has a size approximately equal to a largest dimension of each of said paint spots.
 12. The cooking appliance door as defined in claim 1, wherein said paint spots are printed on said inner door pane.
 13. The cooking appliance door as defined in claim 1, wherein said paint spots are printed on said inner door pane by a screen printing technique.
 14. A cooking appliance comprising a cooking compartment with an opening for introducing cooking materials; and a cooking appliance door for closing said opening of the cooking compartment; wherein said cooking appliance door comprises an inner door pane of borosilicate glass and at least one paint layer applied to a surface on one side of said inner door pane, wherein said at least one paint layer comprises high-temperature-resistant non-enamel paint with an organic or inorganic binder and said at least one paint layer consists of a plurality of individual paint spots each having a predetermined maximal geometric shape, wherein said individual paint spots are arranged in a predetermined pattern with a predetermined paint-free spacing from each other on said surface on said one side of said inner door pane.
 15. The cooking appliance as defined in claim 14, wherein said shape of each of said paint spots is circular, oval, rectangular or irregular, said paint spots each have a largest dimension in a range from 1 to 5 mm and said paint-free spacing between said paint spots has a size approximately equal to said largest dimension of each of said paint spots.
 16. The cooking appliance as defined in claim 14, wherein said predetermined pattern is in the form of a grid comprising a plurality of rows of said paint spots arranged one above the other.
 17. The cooking appliance as defined in claim 14, wherein said predetermined pattern is in the form of an irregular line-shaped pattern. 